Compared with the growing applications of peritectic alloys,none research on the fluid permeability K of dendritic network during peritectic solidification has been reported before.The fluid permeability K of dendriti...Compared with the growing applications of peritectic alloys,none research on the fluid permeability K of dendritic network during peritectic solidification has been reported before.The fluid permeability K of dendritic network in the mushy zone during directional solidification of Sn-Ni peritectic alloy was investigated in this study.Examination on the experimental results demonstrates that both the temperature gradient zone melting(TGZM)and Gibbs-Thomson(G–T)effects have obvious influences on the morphology of dendritic network during directional solidification.This is realized through different stages of liquid diffusion within dendritic mushy zone by these effects during directional solidification.The TGZM effect is demonstrated to play a more important role as compared with the G–T effect during directional solidification.Besides,it is shown that the evolution of dendrite network is more complex during peritectic solidification due to the involvement of the peritectic phase.Through the specific surface SV,analytical expression based on the Carman–Kozeny model was proposed to analyze the fluid permeability of dendritic mushy zone in directionally solidified peritectic alloys.In addition,it is interesting to find a rise in permeability K after peritectic reaction in both theoretical predication and experimental results,which is different from that in other alloys.The theoretical predictions show that this rise in fluid permeability K after peritectic reaction is caused by the remelting/resolidification process on dendritic structure by the TGZM and G–T effects during peritectic solidification.展开更多
The match relationship between rail and wheel was studied by investigating the behavior of the contact fatigue wear in rail/wheel systems.The hardnesses of samples were close or equal to that of the real rail and whee...The match relationship between rail and wheel was studied by investigating the behavior of the contact fatigue wear in rail/wheel systems.The hardnesses of samples were close or equal to that of the real rail and wheel.Meanwhile the probe of study went further into the condition match and the material match based on the hardness match.The experimental results show that the wear rate depends on the hardness ratio(H/H)between rail and wheel,and the safe value of H/Hequals 1.00-11.20.The fatigue life of materials relies on the operating conditions except hardness.The selected experimental conditions satisfy the condition match except Rheat-treated out-line.The factor H/Sis the main element effecting wears in rail steel and wheel steel.The nature of the hardness match is the microstructure match under specified operating conditions.展开更多
The temperature in the high-pressure high-temperature(HPHT) synthesis is optimized to enhance the thermoelectric properties of high-density Zn O ceramic, Zn_(0.98)Al_(0.02)O. X-ray diffraction, scanning electron micro...The temperature in the high-pressure high-temperature(HPHT) synthesis is optimized to enhance the thermoelectric properties of high-density Zn O ceramic, Zn_(0.98)Al_(0.02)O. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy show that HPHT can be utilized to control the crystal structure and relative density of the material.High pressure can be utilized to change the energy band structure of the samples via changing the lattice constant of samples, which decreases the thermal conductivity due to the formation of a multi-scale hierarchical structure and defects. The electrical conductivity of the material reaches 6×10^(4) S/m at 373 K, and all doped samples behave as n-type semiconductors. The highest power factor(6.42 μW·cm^(-1)·K^(-2)) and dimensionless figure of merit(z T = 0.09) are obtained when Zn_(0.98)Al_(0.02)O is produced at 973 K using HPHT, which is superior to previously reported power factors for similar materials at the same temperature. Hall measurements indicate a high carrier concentration, which is the reason for the enhanced electrical performance.展开更多
基金financially supported by the project from the Natural Science Foundation of China(No.51871118)the 2018 Joint Foundation of Ministry of Education for Equipment Pre-research(No.6141A020332)+3 种基金the Key Research and Development Plan of Gansu Province(No.18YF1GA102)the Fundamental Research Funds for the Central Universities(No.lzujbky-2019-sp03)the fund of Science and Technology Project of Lanzhou City(No.2019-1-30)the fund of State Key Laboratory of Special Rare Metal Materials(No.SKL2020K003)。
文摘Compared with the growing applications of peritectic alloys,none research on the fluid permeability K of dendritic network during peritectic solidification has been reported before.The fluid permeability K of dendritic network in the mushy zone during directional solidification of Sn-Ni peritectic alloy was investigated in this study.Examination on the experimental results demonstrates that both the temperature gradient zone melting(TGZM)and Gibbs-Thomson(G–T)effects have obvious influences on the morphology of dendritic network during directional solidification.This is realized through different stages of liquid diffusion within dendritic mushy zone by these effects during directional solidification.The TGZM effect is demonstrated to play a more important role as compared with the G–T effect during directional solidification.Besides,it is shown that the evolution of dendrite network is more complex during peritectic solidification due to the involvement of the peritectic phase.Through the specific surface SV,analytical expression based on the Carman–Kozeny model was proposed to analyze the fluid permeability of dendritic mushy zone in directionally solidified peritectic alloys.In addition,it is interesting to find a rise in permeability K after peritectic reaction in both theoretical predication and experimental results,which is different from that in other alloys.The theoretical predictions show that this rise in fluid permeability K after peritectic reaction is caused by the remelting/resolidification process on dendritic structure by the TGZM and G–T effects during peritectic solidification.
基金Project Supported by the Economy&Trade Committee of China(950130440A)
文摘The match relationship between rail and wheel was studied by investigating the behavior of the contact fatigue wear in rail/wheel systems.The hardnesses of samples were close or equal to that of the real rail and wheel.Meanwhile the probe of study went further into the condition match and the material match based on the hardness match.The experimental results show that the wear rate depends on the hardness ratio(H/H)between rail and wheel,and the safe value of H/Hequals 1.00-11.20.The fatigue life of materials relies on the operating conditions except hardness.The selected experimental conditions satisfy the condition match except Rheat-treated out-line.The factor H/Sis the main element effecting wears in rail steel and wheel steel.The nature of the hardness match is the microstructure match under specified operating conditions.
基金Project supported by the National Natural Science Foundation of China(Grant No.51171070)the Project of Jilin Science and Technology Development Plan,China(Grant No.20170101045JC)。
文摘The temperature in the high-pressure high-temperature(HPHT) synthesis is optimized to enhance the thermoelectric properties of high-density Zn O ceramic, Zn_(0.98)Al_(0.02)O. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy show that HPHT can be utilized to control the crystal structure and relative density of the material.High pressure can be utilized to change the energy band structure of the samples via changing the lattice constant of samples, which decreases the thermal conductivity due to the formation of a multi-scale hierarchical structure and defects. The electrical conductivity of the material reaches 6×10^(4) S/m at 373 K, and all doped samples behave as n-type semiconductors. The highest power factor(6.42 μW·cm^(-1)·K^(-2)) and dimensionless figure of merit(z T = 0.09) are obtained when Zn_(0.98)Al_(0.02)O is produced at 973 K using HPHT, which is superior to previously reported power factors for similar materials at the same temperature. Hall measurements indicate a high carrier concentration, which is the reason for the enhanced electrical performance.
